OBJECTIVETo study micro morphology and element-mixing distribution of different alloys welded in laser and analyze the feasibility of laser welding different alloys.

METHODSAlloys and titanium were matched into 4 groups: Au-Pt with Ni-Cr; Au-Pt with pure Ti; pure Ti with Ni-Cr; Ni-Cr with Co-Cr. They were welded in laser. Changes in metallography after hybridization of crystalline grain, ranges of heat-affected zone and pores were observed through SEM with ultra-thin windowed X-ray energy atlas. Meanwhile 10 testing points were chosen with area of 300 micro m x 900 micro m along the welding surface from the side A alloy to the side B alloy, than the element mixing distribution and tendency were analyzed with X-ray energy atlas.

RESULTS1. Hybridization of different alloys: (l) in the group of Au-Pt with Ti, there was titanium element mixing into Au-Pt tissue gradually and evenly on the Au-Pt side of the interface without clear boundary and increasing in size of crystalline grain. However, there was titanium crystalline grain increasing in size, irregular morphology and small sacks on the titanium side with clear boundary. (2) in the group of Ni-Cr with Ti, there was mixing regularly, slow transition and interlocks between crystalline grains on the Ni-Cr side of the in terface. Poor transition, clear boundary and small cracks were observed on titanium side. (3) in the group of Co-Cr with Ni-Cr, there was good transition, obscure boundary on both sides resulting from network, cylinder and branch structure growing. 2. Element-mixing distribution of different alloys. In fusion zone, the metal elements in matched groups mixed well and hybridized into new alloys except titanium blocks. The location of wave peak depended on the composition of alloys. Most of elements were from the alloy far from the fusion zone.

CONCLUSIONThe hybridization between pure titanium and any other alloys is not good The effect of laser welding different alloys is ideal except with pure titanium.

Alloys ; Chromium Alloys ; chemistry ; Dental Alloys ; chemistry ; Dental Soldering ; Titanium ; chemistry ; Welding

OBJECTIVETo study the bonding characteristic of Titanium and RG experiment porcelain.

METHODS5 specimens with a size of 10 mm x 5 mm x 1.4 mm were cast from pure titanium. Then 1 mm of RG experiment opaque and body porcelain were fused on the surface of the titanium specimens. The interface of titanium and porcelain was analyzed with a scanning electron microscope with energy-despersive spectrometry; 6 metal specimens with the size of 25 mm x 3 mm x 0.5 mm were cast from Ni-Cr alloy and a uniform thickness of 1 mm of VMK 99 porcelain was veneered on the central area of 8 mm x 3 mm 18 metal specimens as the same size were cast from pure titanium. The uniform thickness of 1 mm of VITA TITANKERAMIK porcelain, of Noritake super porcelain Ti-22 and of RG experiment porcelain were veneered on every 6 specimens respectively in the central area of 8 mm x 3 mm. The specimens were subjected to a three-point bending test on a load-test machine with a span of 20 mm, then the failure loads were recorded and statistically analysised. The RG porcelain/titanium crown was fabricated by fusing RG opaque porcelain and body porcelain to cast titanium substrate crown.

RESULTSThe SEM results show no porosity and crackle were found in the interface. The energy-dispersive spectrometry show that there are Si, Ti and O in the 1 micro m layer between porcelain and titanium, which suggesting titanium and experiment porcelain bonding well. The three point test showed the fracture force for the combinations of titanium/VITA TITANKERAMIK porcelain, titanium/Noritake super porcelain Ti-22 and titanium/RG experiment porcelain were (7.233 +/- 2.539) N, (5.533 +/- 1.199) N and (6.316 +/- 1.433) N respectively. There were not statistically significant differences among them (t test, P < 0.01). The fracture force for the Ni-Cr alloy/VMK99 porcelain combination (12.733 +/- 3.297) N was significantly greater than those of the cast titanium/porcelain (t test, P > 0.05). The crown was translucent with no crack.

CONCLUSIONRG porcelain is well compatible with titanium.

Dental Porcelain ; chemistry ; Metal Ceramic Alloys ; chemistry ; Titanium ; chemistry

OBJECTIVETo investigate the effect of pH value and fluoride ions on the corrosion resistance of pure Ti and Ni-Cr-Ti alloy in the artificial saliva.

METHODSElectrochemical technique was used to measure the electric potential of corrosion (Ecorr), current density of corrosion (Icorr) and polarization resistance (Rp) of pure titanium and Ti-Ni-Cr alloy in the artificial saliva with different pH value and fluoride concentrations. After electrochemical analysis, microstructure and phase diffraction were examined by FSEM.

RESULTSWith the lower pH value, the Ecorr and Icorr of pure titanium and Ti-Ni-Cr alloy increased, the Rp decreased, there was a significant difference (P<0.05). The Ecorr and Icorr increased markedly, the Rp significantly reduced in the artificial saliva containing 0.2% NaF (P<0.01). FSEM showed that pure titanium and Ti-Ni-Cr alloy surface corrosion, pure titanium in the artificial saliva containing 0.2% NaF was most serious.

CONCLUSIONLower pH value decreases the corrosion resistance of pure titanium and Ti-Ni-Cr alloy and the artificial saliva containing fluoride ions decreases the corrosion resistance of pure titanium.

Chromium Alloys ; chemistry ; Corrosion ; Dental Alloys ; chemistry ; Electrochemistry ; Fluorides ; chemistry ; Hydrogen-Ion Concentration ; Materials Testing ; Metal Ceramic Alloys ; chemistry ; Nickel ; chemistry ; Saliva, Artificial ; chemistry ; Surface Properties ; Titanium ; chemistry

Ceramics ; Dental Alloys ; chemistry ; Dental Porcelain ; Dental Restoration, Permanent ; Humans ; Metal Ceramic Alloys ; chemistry

OBJECTIVETo investigate the change of retentive forces of cast cobalt-chromium (Co-Cr) alloy clasp in cyclic fatigue test.

METHODSSamples of three types of cast Co-Cr alloy (Group A: Hardalloy; B: Regalloy™; C: Vera PDN™) clasps were fabricated and placed at undercut depths of 0.25 mm, 0.50 mm. The clasps were drawn from the model molar cyclicly to simulate 5 years of clinical use in an universal testing machine. Retentive force were record at 21 different time point for each clasp during the whole fatigue testing process. Data were subjected to ANOVA, Chi-square test and linear regression analysis.

RESULTSAll clasps showed decreasing retention during the cyclic fatigue test. Clasps engaged in 0.50 mm undercut depth exhibited greater initial retentive force [Group A: (8.714 +/- 1.104) N, B: (9.072 +/- 0.653) N, C: (9.588 +/- 1.980) N] as well as greater loss of retention [Group A: (4.408 +/- 0.662) N, B: (3.484 +/- 0.494) N, C: (3.290 +/- 1.484) N] at the end of the test than clasps engaged in 0.25 mm undercut did [initial forces were (7.940 +/- 0.357), (7.834 +/- 1.308) and (8.156 +/- 1.067) N for Group A, B, C, respectively; loss of retention were (2.444 +/- 0.736) N, (2.954 +/- 1.048) N and (1.832 +/- 1.180) N for group A, B, C, respectively]. Negative correlation was found between the clasp retention and the logarithm of cycling times.

CONCLUSIONSCo-Cr alloy cast clasp could provide adequate retentive force for 5 years of clinical use.

Chromium Alloys ; chemistry ; Dental Alloys ; chemistry ; Dental Casting Technique ; Dental Clasps ; Dental Stress Analysis ; Denture Retention

OBJECTIVETo evaluate the effect of aurum coating on corrosion resistance of Ni-Cr alloy in artificial saliva environment.

METHODSThe corrosion potential (E(corr)), self-corrosion current density (I(corr)), and polarization resistance (R(p)) of three alloys were measured using electrochemical methods to compare the difference of corrosion resistance between aurum-coated Ni-Cr alloy and Ni-Cr alloy or Au alloy. Meanwhile, microstructural and phase diffraction was examined with field scanning electromicroscopy (FSEM) and surface chemical analysis was performed by energy diffraction X-ray (EDX).

RESULTSThe I(corr) of aurum-coated Ni-Cr alloy was (0.70 +/- 0.20) x 10(-6) A/cm2, which was significantly higher than that of Au alloy (P < 0.05) and lower than that of Ni-Cr alloy (P < 0.05). R(p) of aurum-coated Ni-Cr alloy was (34.77 +/- 12.61) KOmega.cm2, which was higher than that of Ni-Cr alloy (P < 0.05) and lower than that of Au alloy (P < 0.05). The results of FSEM showed that the corrosion resistance of Ni-Cr alloy coated with aurum was better than that of Ni-Cr alloy. The results of EDX indicated that released Ni and Cr of Ni-Cr alloy coated with aurum after test were less than those of Ni-Cr alloy (P < 0.05).

CONCLUSIONSThe corrosion resistance of aurum-coated Ni-Cr alloy is higher than that of Ni-Cr alloy.

Chromium Alloys ; chemistry ; Corrosion ; Electrochemistry ; Gold Alloys ; chemistry ; Metal Ceramic Alloys ; chemistry ; Microscopy, Electron, Scanning ; Nickel ; chemistry ; Saliva, Artificial ; chemistry ; Surface Properties

The dissolution of nickel from nitinol alloy under different extraction conditions was investigated when biological tests of nitinol medical devices were carried out. It discussed the equivalence of these extraction conditions and found the best extraction conditions. In the experiment, two brands of nitinol were chosen and extracted under different extraction conditions according to GB/T 16886-12. Plasma emission spectrometer was used to analyse the concentration of nickel in extract liquid. The results show that there is no equivalence among these extraction conditions for nitinol materials. And it is suggested that (37 +/- 1) degree C, (72 +/- 2) h could be used as normal extraction condition and (70 +/- 2) degrees C, (24 +/- 2) h as accelerated extraction condition.
Alloys ; chemistry ; Biocompatible Materials ; Materials Testing ; Nickel ; chemistry ; Temperature ; Titanium

OBJECTIVEThe aim of this study was to establish sol-gel technique of coating titanium on the surface of Ni-Cr alloy (PFM) in order to enhance corrosion resistance and reduce corrosive rate in oral cavity.

METHODSThe sol-gel technique included four steps: (1) pre-treatment; (2) preparation of sol; (3) coating; (4) heat treatment. Elements on the surface of Ni-Cr alloy were analyzed with X-ray photoelectron spectroscopy.

RESULTSAfter coating Ti, the surface of Ni-Cr alloy looked light golden without particles, blisters and fragments. Besides Ni and Cr, titanium was found on surface of Ni-Cr alloy after coating. With Ar(+) ion carving-corrosion figure, the thickness of titanium was about 20 - 80 microm.

CONCLUSIONWith sol-gel technique, titanium could be coated on the surface of Ni-Cr alloy.

Chromium Alloys ; chemistry ; Coated Materials, Biocompatible ; Dental Alloys ; chemistry ; Dental Materials ; Gels ; Humans ; Materials Testing ; methods ; Nickel ; chemistry ; Titanium ; chemistry

Exposed to neutron flow, the phosphorus implanted TiNi alloy gets radioactive. This radioactive material is used in vascular stent for prevention and cure of restenosis. Phosphorus implantation is carried out in a plasma immerged ion implantation system, and the dose of phosphorus implantation is in the range of 2-10 x 10(17) cm-2. After ion implantation, the alloy is exposed to the slow neutron flow in a nuclear reactor, the dose of the slow neutron is 1.39-5.88 x 10(19) n/cm2. The radioactivity of the TiNi alloy was measured by liquid scintillation spectrometry and radio-chromic-film dosimetry. The result shows that whether the phosphorus is implanted or not, the TiNi alloy comes to be radioactive after exposure to neutron flow. Just after neutron irradiation, the radiation dose of phosphorus implanted TiNi alloy is about one hundred times higher than that of un-phosphorus implanted TiNi alloy. The radiation difference between phosphorus and un-phosphorus implanted alloy decreases as time elapses. Within three months after neutron irradiation, the average half-decay period of phosphorus implanted TiNi alloy is about 62 days. The radiation ray penetration of phosphorus implanted TiNi alloy is deeper than that of pure 32P; this is of benefit to making radiation uniformity between stent struts and reducing radiation grads beyond the edge of stent.
Alloys ; chemistry ; Blood Vessel Prosthesis ; Nickel ; chemistry ; Phosphorus Radioisotopes ; chemistry ; Radiation Dosage ; Titanium ; chemistry

The recovery force of Ti-Nb coated and uncoated TiNi shape memory alloy rods was investigated. The rods were 6.0 mm, 6.5 mm and 7.0 mm in diameter respectively. The mean transition temperature was 33.0 degrees C. The rods were stored at -18 degrees C and pre-bent with a three-point bending fixture, the span was 20. 0 centimeters and the deflections were 5.0 mm, 10.0 mm, 15.0 mm and 20.0 mm, respectively. The rods were then heated in a constant temperature saline solution chamber. The experimental temperature was 37.0 C and 50.0 C respectively. The recovery force was measured in a constant displacement mode on biomaterial test machine. The results showed that the recovery force of the memory alloy rod increased with increasing recovery temperature, rod diameter and deformation of both Ti-Nb coated and uncoated surface. The recovery force of Ti-Nb coated rods of 6.0 and 6.5 millimeter in diameter was lower than the uncoated rods in the same diameter. However, the recovery force of 7.0-mm-diameter rods showed no significant difference between coated and uncoated surface.
Alloys ; chemistry ; Biomechanical Phenomena ; Coated Materials, Biocompatible ; Niobium ; Temperature ; Titanium